Double back swing seat



FIG. 1 is a front elevational view of a double back swing seat showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a top perspective view thereof rotated 90° from the left of FIG. 1; and

FIG. 8 is a bottom perspective view thereof rotated 90° from the left of FIG. 6. 

The ornamental design for a double back swing seat, as shown and described. 